This application claims the priority benefit of Taiwan application serial no. 89101459, filed Jan. 28, 2000.
1. Field of the Invention
The invention relates to preparation of cyanine dye. More particularly, the present invention relates to preparation of cyanine dye for a high density optical recording disk.
2. Description of the Related Art
There is at present an extreme need for a storage medium with higher storage density, smaller size and lower cost. As magnetic storage medium is not able to meet these requirements, organic media are highly sought after as an alternative. Organic dye which combines the advantages and characters of both the photosensitizer and photorecording medium, has been highly developed and adopted by the optoelectronic industry. The applications of organic dye include the fields of, for example, nonlinear optical devices, recording and displaying of optical disc data, photoresists, sensors and indicators for heat, light, and electrons during the transfer and storage of energy, medicine and biology, etc.
An organic dye, cyanine blue, was first synthesized by Greville Williams in 1856 (K. Venkataraman (ed.), The Chemistry of Synthetic Dyes, Vol. II, p.1143-1186, Academic Press, New York, 1952.). In 1875, Vogel discovered that Cyanine Blue has special photosensitive properties. Therefore, cyanine blue, which was originally used as a colorant, became a photosensitizer with a greater value. Different structures of cyanine dye have different xcexmax which varies from UV to IR. Therefore, cyanine blue can also serve as photosensitizer for photoresists or optical storage media in the electronic industry as well as being a colorant.
Cyanine dye, 3,3xe2x80x2-diethyl-12-acetyl-thiatetracyanine perchlorate, was first proposed for use in optical disc fabrication by Law et al. (K. Y. Law, P. S. Vincett, and G. E. Johnson, Appl. Phys. Lett., 39, 718(1981)). The cyanine dye and PVAc (poly(vinyl acetate)) were first mixed and then spin-coated to form an optical recording medium. After this successful use, several kinds of cyanine were developed for optical disc applications, such as those disclosed in U.S. Pat. Nos. 5,019,476, 5,292,615, 5,328,802, 5,332,608, 5,424,171, 5,455,094, 5,900,348, 5,958,087 etc. As to the method of fabrication, it was found that spin coating of the dye on the substrate could shorten the process and reduce costs when compared with the chemical vapor deposition (CVD) process; therefore spin coating has been accepted as the standard procedure and the stability of the organic dye and its solubility in organic solvent are critical factors for successful results.
It is therefore an object of the invention to provide cyanine dye (I) with xcexmax in the visible light range (500 nm-650 nm) for use as a high density optical disc recording medium. This cyanine dye is thermally stable for laser writing and has a good solubility in organic solvent. The cyanine dye of this invention has a high recording sensitivity and signal-to-noise ratio (S/N) value.
This invention uses indolenine having a side chain 
with a pull electrons effect on nitrogen such that the cyanine dye is thermally stable and has a good solubility in organic solvent.
The formula for cyanine in this invention is shown as structure formula (I): 
wherein R1 represents 
R2 represents alkyl with C1-C18 or 
and n is 1. For cyanine dye (II) and (III), Xxe2x88x92 is halogen anion (such as Clxe2x88x92, Brxe2x88x92, Ixe2x88x92 etc.), alkylsulfate anion (such as CH3SO4xe2x88x92, C2H5SO4xe2x88x92 etc.), arylsulfonate anion 
perchlorate anion (such as ClO4xe2x88x92 etc.), TCNQxe2x88x92, PF6xe2x88x92 or BF4xe2x88x92.
The structural formula (II) of cyanine dye, 2-[3-(1,3dihydro-1,1-dimethyl-3(4xe2x80x2-methoxycarbonyl)benzyl)-2H-benze[e]indol-2-ylidene]-1-propenyl]1,1-dimethyl-3butyl-1H-indolium perchlorate(E03-SL1), in one embodiment of this invention and is shown as follows: 
Preparation of dye (II) is described as follows. A mixed solution 4-chloromethylbenzoyl chloride (1.5-2.5 g, preferably 1.89 g) and methanol (0.3-0.4 g, preferably 0.32 g) is first dissolved in benzene (20-30 ml, preferably 25 ml). Pyridine (0.7-0.85 g, preferably 0.791 g) is then added to this mixture and heated to 40-50xc2x0 C. (preferably 45xc2x0 C.) for several hours to obtain methyl(4-iodomethyl)benzoate(MIB). MIB (2.5-3 g, preferable 2.76 g) and 2,3,3-trimethyl-4,5-benzo-3H-indole (1.5-2 g, preferably 1.75 g) are dissolved in benzene and heated for several hours such that 1-(4xe2x80x2-methoxycarbonyl)benzyl-2,3,3-trimethyl-4,5-benzo-3H-indolium iodide(MBTI) is obtained. 1-Iodobutane (2.5-3 g, preferably 2.76 g) and 2,3,3-trimethyl indolenine (2-2.5 g, preferably 2.38 g) are dissolved in benzene and heated for several hours (preferably 4 hours) to obtain 1-butyl-2,3,3-trimethyl indolenine(BII). MBTI (2.5-3 g, preferably 2.77 g) and N,Nxe2x80x2-diphenylformamidine (1-1.5 g, preferably 1.12 g) are dissolved in acetic anhydride (15-25 ml, preferably 20 ml) and heated for several hours to obtain BFEI. BII (3-4 g, preferably 3.2 g), BFEI (6-7 g, preferably 6.5 g) and sodium acetate (0.5-1 g, preferably 0.82 g) are heated to 95-105xc2x0 C. (preferably 100xc2x0 C.) in acetate anhydride (preferably 50 ml) for several hours. Then, iodine is replaced by sodium perchlorate to abtain E03-SL1.
The structural formula (III) of cyanine dye, 2-[3-(1,3dihydro-1,1-dimethyl-3(4xe2x80x2-methoxycarbonyl)benzyl-2H-benze[e]indol-2-ylidene]-1-propenyl]1,1-dimethyl-3(4xe2x80x2-methoxycarbonyl)benzyl-1H-indolium perchlorate(E03-SL2), in another embodiment of this invention is shown as follows: 
Preparation of dye (III) is described as follows. A mixed solution of 4-chloromethylbenzoyl chloride (1.5-2.5 g, preferably 1.89 g) and methanol (0.3-0.4 g, preferably 0.32 g) is first dissolved in benzene (20-30 ml, preferably 25 ml). Pyridine (0.7-0.85 g, preferably 0.791 g) is then added to this mixture and heated to 40-50xc2x0 C. (preferably 45xc2x0 C.) for several hours to obtain methyl(4-iodomethyl)benzoate (MIB). MIB (2.5-3 g, preferable 2.76 g) and 2,3,3-trimethyl-4,5-benzo-3H-indole (1.5-2 g, preferably 1.75 g) are dissolved in benzene to heat for several hours such that 1-(4xe2x80x2-methoxycarbonyl)benzyl-2,3,3-trimethyl-4,5-benzo-3H-indolium iodide (MBTI) is obtained. MIB (2.5-3 g, preferably 2.76 g) and 2,3,3-trimethyl indolenine (1.3-2 g, preferably 1.59 g) are dissolved in benzene and heated for several hours to obtain 1-(4xe2x80x2-methoxycarbonyl)benzyl-2,3,3-trimethyl indoleninium (MBII). MBTI (2.5-3 g, preferably 2.77 g) and N,Nxe2x80x2-diphenylformamidine (1-1.5 g, preferably 1.12 g) are dissolved in acetic anhydride (15-25 ml, preferably 20 ml) and heated for several hours to obtain BFEI. MBII (4-4.5, preferably 4.15 g), BFEI (6-7 g, preferably 6.5 g) and sodium acetate (0.5-1 g, preferably 0.82 g) are heated to 95-105xc2x0 C. (preferably 100xc2x0 C.) in acetate anhydride (preferably 50 ml) for several hours. Then, iodine is replaced by sodium perchlorate to obtain E03-SL2.
The cyanine dye of the invention is applicable for recording discs and can further include cyanine dye such as 1-(4xe2x80x3-methoxycarbonyl) benzyl-3,3-dimethyl-1xe2x80x2-(4xe2x80x3-methoxycarbonyl)benzyl-3xe2x80x2,3xe2x80x2-dimethyllindo-2:2xe2x80x2-pentamethine perchlorate(E05)(IV) for use as a photosensitizing dye, thereby raising reflectivity of recording disc.
When the mixture of dye (I) and dye (IV) is used, the weight percentage of dye (I) to the total make-up solution can be 1%-10% and the weight percentage of dye (IV) to dye (I) is preferably 3.5%-5%.
The dyes in this invention can be dissolved in an alcohol (such as methanol, ethanol, isopropanol, etc.), a ketone (such as acetone, methyl-ethyl ketone (MEK), etc.), an ether (such as ethyl ether, tetrahydrofuran, etc.), chloroform or dichloromethane. Thereafter, the dyes can be coated onto a blanket polycarbonate (PC) substrate by a spin coater through spray, roll-coating, immersion or spin-coating. In addition, cyanine dye not only serves as a photorecording medium but also as a photosensitizer for photography, transcription or printing.
When the mixture including dye (I), dye (IV) and solvent is used, the weight percentage of dye (I) to the total make-up solution can be 0.5%-7% and preferably 1%-3%.